The proposed research seeks to examine operant conditioning (biofeedback) schedules in order to delineate the nature and extent to which such procedures can be used to reliably reduce blood pressure in intact baboons. Because it has been difficult to achieve blood pressure lowering from resting, normotensive levels, blood pressure levels will be elevated prior to the lowering procedure by infustions of hypertonic saline into the circulation. This method has been shown in pilot data to increase both systolic and diastolic pressures. The salt infusions will not only provide an elevated baseline of blood pressure, but will also provide information about the effects of high salt intake on circulatory parameters in the intact primate. The exact procedure will use chair restrained baboons with chronic indwelling arterial and venous catheters. Daily infusions of 5% hypertonic saline into the circulation will be given at 15 gm/day. Once blood pressures are elevated by approximately 20 mmHg, operant conditioning procedures involving the reinforcement of decreases in diastolic blood pressure will be instituted while salt loading is ongoning. Once stable decreases in blood pressure are achieved, environmental scheduling and stimulus feedback parameters will next be examined in relation to the generalization of learned blood pressure decreases beyond the session periods. Systolic and diastolic blood pressures, heart rate, water intake, and plasma catecholamine levels will be monitored throughout. These investigations seek to develop and refine an area that has evaded systematic and rigorous laboratory research. The development of learning techniques for lowering blood pressure will find ultimate application with patients who are hypertensive and do not elect pharmacological treatments as a method of choice, or do not respond well to drug regimens. The investigation of maintaining the blood pressure decreases beyond the session hours addresses the problem of blood pressure control outside of the biofeedback clinic. The role of sympathetic nervous activity in the learned production of blood pressure decreases will be assessed by determinations of catecholamine levels in these baboon subjects.